GridStor bought a ready-to-build battery project in Galveston County, Texas, from Balanced Rock Power in March 2024. At announcement it was a 450 MW, 900 MWh project called Evelyn. A month later the grid queue listed it at 220 MW. The asset GridStor actually built is less than half the one it announced, and that changes what the deal was worth.
Key takeaways
- GridStor announced on 7 March 2024 that it had acquired the Evelyn battery energy storage project in Galveston County, Texas, from Balanced Rock Power, a ready-to-build project located near the Hidden Lakes substation owned by Texas New Mexico Power.
- The Evelyn battery was announced at 450 MW and 900 MWh, but the April 2024 update to the ERCOT interconnection queue listed the project, renamed Hidden Lakes BESS, at 220 MW, and Enerdatics revised the deal to 220 MW and 440 MWh, a two-hour battery.
- The parties did not disclose a price for GridStor's acquisition of Hidden Lakes; Enerdatics estimates the consideration at $15 million, or about $0.07 million per MW on the revised 220 MW capacity.
- Enerdatics records an investment of $177 million in the Hidden Lakes BESS, a financial close on 17 October 2024 and commercial operation on 4 November 2025.
- GridStor funded Hidden Lakes with a $74 million construction loan from First Citizens Bank, announced in March 2025, and an $86 million sale of investment tax credits to Foss & Company, announced in November 2025.
What changed between the announcement and the build?
The size. When GridStor announced the purchase, the project was described as 450 MW with 900 MWh of storage, due to start construction in the third quarter of 2024 and finish in the second quarter of 2025. The ERCOT interconnection data published in March 2024 still showed 450 MW. The April 2024 update showed 220 MW.
An interconnection queue is the list a grid operator keeps of projects asking to connect, with the capacity each one has requested. It is the most reliable public record of what a project will actually inject into the grid, which is why Enerdatics revised the deal to follow it. The records do not say why the project was cut. They show only that the reduction came within weeks of the sale.
The duration did not change. A battery's duration is its energy capacity divided by its power rating. At 450 MW and 900 MWh, Evelyn was a two-hour battery. At 220 MW and 440 MWh, Hidden Lakes is still a two-hour battery. The project shrank in proportion rather than being reshaped.
What does the downsizing do to the price per MW?
It roughly doubles it. Enerdatics' estimate of about $15 million works out at roughly $0.07 million per MW on 220 MW. Spread across the 450 MW the project was announced at, the same sum would have been about $0.03 million per MW.
For a project that has not been built, that figure is best read as a developer premium: the price paid for permits, land, a grid position and engineering work, before any batteries are bought. The capital cost comes later. Here it came to $177 million, more than eleven times the estimated purchase price.
That ratio is the point of buying at ready-to-build. GridStor paid a small sum for the right to spend a large one, and the small sum bought a shorter path to operation. The project sits next to an existing substation, which the companies said would let the batteries begin grid-connected operations quickly.
How was Hidden Lakes paid for once it was bought?
With bank debt during construction and tax credits at completion. Financial close came on 17 October 2024, seven months after the purchase. The $74 million First Citizens Bank construction loan was announced in March 2025. The $86 million sale of investment tax credits to Foss & Company followed in November 2025, a week after the project began operating.
Tax credit transfer lets a project owner sell federal investment tax credits to a third party for cash, rather than using them itself or bringing in a tax equity partner. Foss & Company has done this before in Texas storage, as in the tax credits Tokyo Gas sold to cover over half of its Longbow battery. At Hidden Lakes the credit sale equals about 49 percent of the $177 million investment Enerdatics records. Together the loan and the credit sale add up to about 90 percent of it, although the records do not say how the two interact or whether the credit proceeds repaid part of the loan.
Enerdatics' data shows how thin the priced market is for Texas batteries. Across 30 battery transactions in Texas announced between January 2023 and June 2025, nine asset deals carry enough information to calculate a value per MW. Their developer premium has a median of $0.04 million per MW and runs from $0.02 million to $0.07 million. At about $0.068 million per MW on its revised capacity, Hidden Lakes sits at the top of that range. Among the four priced ready-to-build Texas deals, the median developer premium is $0.07 million per MW, which puts Hidden Lakes in line with its stage. On the original 450 MW, at about $0.03 million per MW, it would have sat below the market median.
What does the deal signal for Texas battery storage?
It signals that a buyer of an unbuilt battery is buying a grid position whose size can still move. A purchase price agreed against an announced capacity can look very different once the queue settles. A price per MW only means something once the connectable capacity is known.
It also signals how storage developers are assembling portfolios. GridStor had already acquired a 500 MW portfolio from Upstream Energy in October 2022. In September 2025 it raised a $50 million letter of credit facility from NORD/LB to support further projects, including GridStor's White Tank battery in Arizona. That is the same pattern UBS followed in Texas, buying unbuilt projects and then raising debt across a portfolio, as in UBS's Texas batteries, from SMT purchase to a $316 million loan.
The demand case is not in doubt. ERCOT anticipates that Texas will need an extra 5 GW of power by 2030 for summer peaks and up to 16 GW for extreme winter conditions. The question each buyer has to answer is how much of that demand a given grid connection can actually serve.
Frequently asked questions
What did GridStor buy from Balanced Rock Power? GridStor acquired the Evelyn battery energy storage project in Galveston County, Texas, announced on 7 March 2024. Now called Hidden Lakes BESS, the project was revised from 450 MW and 900 MWh to 220 MW and 440 MWh after the April 2024 ERCOT queue update.
How much did GridStor pay for Hidden Lakes? The price was not disclosed by the companies. Enerdatics estimates the consideration at $15 million, about $0.07 million per MW on the revised 220 MW capacity.
When did Hidden Lakes start operating? Enerdatics records commercial operation of the Hidden Lakes BESS on 4 November 2025, after financial close on 17 October 2024 and a total investment of $177 million.
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